Various physiologic signals are often recorded and analyzed. These signals may included digestive pH, various digestive motility and pressure signal, EEG and EMG, to list only a few.
Typically, physicians require the concurrent recording a variety of physiologic signals. For example, gastric pH is often collected at the same time as pressure. Through the concurrent collection of various parameters the physician may better understand the patient's condition.
Ambulatory recording and recorders are widely used. Such devices include the Digitrapper Mk III.TM. ambulatory recorder from Synectics Medical AB, the GastroScan II.TM. from Medical Instruments Corporation, and the SuperLogger.TM. from Sandhill Scientific. These types of devices make it possible for patients to remain at home, or at the least be ambulant in a hospital setting while physiological data is recorded. Typically the devices comprise a lightweight recorder in which the desired physiological data signals are temporarily stored and later downloaded for future analysis.
Many types of physiological data may be recorded, including ECG (Electrocardiogram), EEG (Electroencephalogram) or pH and pressure (Motility) in the gastrointestinal tract. Preferably such a recorder should be able to record among a programmable number of channels at a variety of programmable frequencies.
Among the problems with current recorders, however, is that of energy usage. Such recorders, because they must be ambulatory, are battery powered.
In the particular situation of ambulatory recorders, the power consideration are further complicated by the variety of channels and frequencies from which data is desired to be sampled.
Devices which sample along a programmable number of channels and a variety of programmable frequencies along each channel present a number of difficulties. Among these difficulties lies in the management of the memory buffer such that a pre determined amount of data in the memory will be subject to possible loss. For example, if the device samples along one channel at a low frequency, the memory will take a great deal of time to be filled. Thus until this transfer takes place, the data in the memory buffer is subject to loss, for example if the device's battery fails and all power is lost.